In an effort to eat healthily we could be poisoning ourselves.
More on the diet theme this week. This time, a cautionary tale about a very popular food – Sushi. Recently, I was at brunch with a good friend of mine, Lisa. I asked her how she was, and she said “Not great. I keep getting headaches – migraines. And I feel like I have early Alzheimer’s. I can’t seem to remember things one day to the next.” We put it down to working in a stressful job and carried on with our eggs Benny. Several weeks later, we had brunch again– same restaurant, eggs Benny again – but now Lisa said she was missing days at work due to her headaches, having nosebleeds, and having trouble concentrating, and keeping in what she ate. In fact, no sooner had she finished her breakfast than she excused herself to go to the toilet. When she came back she confessed to having lost ‘everything.’ I’ll spare you the gory details.
We both thought this had to be more than just stress, so Lisa went to see her doctor, who tested her for mercury toxicity. It turned out that she was eating Tuna – canned light Tuna – every day – in salad, as well has having Tuna sushi on a regular basis. Lisa is on a diet and is very careful about what she eats (except when we have brunch together). She understood that Tuna is good for you – essential fatty acids- low in fat, good source of protein. But Tuna, including canned light Tuna and albacore Tuna, contain mercury. If eaten frequently enough, as Lisa was doing, the levels will build up in your body and become toxic.
Lisa had mercury levels in her blood twice that of normal. She was the third female patient her doctor had seen over several months who had mercury toxicity. Her doctor’s advice? ‘Stop eating Tuna and you will start to feel better in about six weeks.’ It’s been just over three weeks and Lisa is already feeling better – the headaches have stopped, and her concentration is improving.
One of the problems with mercury toxicity is that the symptoms are so general you could put them down to any number of things – like stress, or the flu, or allergies. The symptoms include:
- Changes in vision or hearing
- Memory problems
- Increases in blood pressure or heart rate
- Eye irritation
- Breathing problems
- Painful mouth
- Abdominal pain
- Fever and/or chills
- Acrodynia – caused by chronic or long-term exposure to mercury. The symptoms for this include itching, swelling, flushing, pink colored palms, excessive perspiration, rashes irritability, fretfulness, sleeplessness, joint pain and weakness.
- Some children may experience trouble learning in school
Having said all this, fish and shellfish are an important part of a healthy diet because they contain good quality protein and essential nutrients including omega 3 fatty acids, and are low in saturated fats. As the Food and Drug Administration (FDA) in the United States points out “nearly all fish and shellfish contain traces of mercury. For most people, the risk from mercury by eating fish and shellfish is not a health concern.”
However, the FDA and the U.S. Environmental Protection Agency (EPA) have posted information on mercury poisoning. They recommend that pregnant women, women of childbearing age, nursing mothers, and young children limit the amount of fish they eat, because of the danger of mercury poisoning.
As of March 2004, the FDA and the EPA advised that women in the above categories avoid Shark, Swordfish, King Mackerel, and Tilefish altogether because they contain high levels of mercury. They also recommend not eating more than 12 ounces— or two meals on average— of fish or shellfish that are lower in mercury, per week and no more than one six ounce can of Tuna per week, or 6 ounces of Lobster, Halibut, or Orange Ruffy.
According to the FDA and the EPA, the following are the five most commonly eaten types of fish, and have low mercury levels:
- Canned light tuna – NOT albacore tuna
The FDA has a good list of frequently asked questions posted on their Website – including information about mercury content in fish sticks. In brief, they say that the fish used in fast food sandwiches and fish sticks contain fish that are low in mercury. And Tuna steaks? The FDA/EPA recommended allowance is six ounces per week.
Currently, there are no guidelines for people who aren’t women of childbearing age, nursing mothers, or children. But if the FDA/EPA guidelines are good enough for these folks, they’re good enough for me – until the FDA or a similar body comes out with scientifically based guidelines for the rest of us.
If you would like to know more about mercury poisoning from fish and shellfish, and other sources, visit the Website for the U.S. Center for Food Safety and Nutrition at:
www.cfsan.fda.gov – go to the Search bar – select ‘mercury’ and click on ‘Go’.
If you have a comment, contact firstname.lastname@example.org
Reviewed January 11, 2009
Reference: U.S. Department of Health and Human Services and the U.S. Environmental Protection Agency: “What you need to know about mercury in fish and shellfish. March 2004, EPA-823-R-04-005.
How does mercury enter the food chain?
Mercury is a natural element – a metal – present in the environment. Activities like farming, manufacturing that uses mercury, and burning coal increase the amount of mercury cycling in our environment. When mercury is introduced to water it turns into methylmercury.
What types of fish contain the highest amounts of mercury?
Large, predatory, long-lived, ocean-going fish have the highest levels of mercury: they consume it through the food chain and the mercury gets stored in their tissues.
How big is a 6 oz serving (170 grams)?
Approximately the size of two decks of regular playing cards.
Related Blog of Interest
Blog for Environmental Defense – a highly rated scientific organization founded 40 years ago.
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